This invention relates to a computer system for handling a virtualized storage region. Computer systems used in banks and stock companies usually make back-up copies of data contained in those computer systems (hereinafter referred to as “backup”) to prevent loss of data due to a failure in the system.
Japanese Patent Laid Open No. 132343/2000 discloses a method in which a copy of data is created in a storage unit system of a computer system (the method herein referred to as a “snapshot”) to back-up the data based on the copied data. There has further been proposed a method of creating a copy of data not in the storage unit system but between the storage unit systems (hereinafter referred to as “remote copy”).
Currently, a tremendous amount of data is processed in computer systems, and the users are bearing increased costs for managing the storage unit systems. A report “Virtualizing the SAN,” published Jul. 5, 2000, by Morgan Keegan, a research company, discloses a system in which storage regions offered by a plurality of storage unit systems in a computer system are virtualized to form a theoretical storage region (virtualized volume), and the virtualized volume is offered to the user (host computer) to decrease the user's cost of managing the storage unit.